This UCLA Symposium will address the molecular pathways of cytokine action. Lymphokines, monokines and other cytokines are critically involved in many stages of differentiation, homeostasis and pathophysiology. Descriptions of the range of cytokine actions upon target and effector cells in inflammation, infectious diseases and neoplasia, for example, continue to increase at a rapid rate. New molecular mediators and additional actions are reported with impressive frequency. Definition of the fundamental nature of these mediators, their mode of action, and their relationships to other intercellular and intracellular molecular events is pivotal to understanding the role of cytokines in health and disease. This meeting will assemble investigators in diverse yet interrelated areas including immunoregulation, cell differentiation and growth control, aging, infectious disease, and oncology to unify our appreciation of pathways by which cytokines exert their influence. It will emphasize roles of cytokines in health and disease and their potential biotherapeutic usefulness.